# -*- coding: utf-8 -*-
#
#--
# Copyright (C) 2009-2010 Thomas Leitner <t_leitner@gmx.at>
# Copyright (C) 2010-2014 Carsten Bormann <cabo@tzi.org>
#
# This file was derived from a part of the kramdown gem which is licensed under the MIT license.
# This derived work is also licensed under the MIT license, see LICENSE.
#++
#
require 'shellwords'

raise "sorry, 1.8 was last decade" unless RUBY_VERSION >= '1.9'

gem 'kramdown', '~> 1.17.0'
require 'kramdown'
my_span_elements =  %w{list figure xref eref iref cref spanx vspace}
Kramdown::Parser::Html::Constants::HTML_SPAN_ELEMENTS.concat my_span_elements

require 'rexml/parsers/baseparser'
require 'open3'                 # for math
require 'json'                  # for math

class Object
  def deep_clone
    Marshal.load(Marshal.dump(self))
  end
end

module Kramdown

  module Parser

    class RFC2629Kramdown < Kramdown

      def initialize(*doc)
        super
        @span_parsers.unshift(:xref)
        @span_parsers.unshift(:iref)
      end

      SECTIONS_RE = /Section(?:s (?:[\w.]+, )*[\w.]+,? and)? [\w.]+/

      def handle_bares(s, attr, format, href)
        sa = s.sub(/\A\S+\s/, '').split(/,? and /)
        sa[0..0] = *sa[0].split(', ')
        sz = sa.size
        if sz != 1         # we have to redo xml2rfc's work here
          @tree.children << Element.new(:text, "Sections ", {}) # XXX needs to split into Section/Appendix
          sa.each_with_index do |sec, i|
            attr1 = {"target" => href, "section" => sec, "sectionFormat" => "bare"}
            @tree.children << Element.new(:xref, nil, attr1)
            text = if i == 0 && sz == 2
                     " and "
                   elsif i == sz-1
                     " of "
                   elsif i == sz-2
                     ", and "
                   else
                     ", "
                   end
            @tree.children << Element.new(:text, text, {})
          end
          # attr stays unchanged, no section added
        else
          attr['section'] = sa[-1]
          attr['sectionFormat'] = format
        end
      end

      XREF_START = /\{\{(?:(?:\{(.*?)\}(?:\{(.*?)\})?)|(\X*?))((?:\}\})|\})/u

      # Introduce new {{target}} syntax for empty xrefs, which would
      # otherwise be an ugly ![!](target) or ![ ](target)
      # (I'd rather use [[target]], but that somehow clashes with links.)
      def parse_xref
        @src.pos += @src.matched_size
        unless @src[4] == "}}"
          warn "*** #{@src[0]}: unmatched braces #{@src[4].inspect}"
        end
        if contact_name = @src[1]
          attr = {'fullname' => contact_name}
          if ascii_name = @src[2]
            attr["asciiFullname"] = ascii_name
          end
          el = Element.new(:contact, nil, attr)
        else
          href = @src[3]
          attr = {}
          if $options.v3
            # match Section ... of ...; set section, sectionFormat
            case href.gsub(/[\u00A0\s]+/, ' ') # may need nbsp and/or newlines
            when /\A(#{SECTIONS_RE}) of (.*)\z/
              href = $2
              handle_bares($1, attr, "of", href)
            when /\A(.*), (#{SECTIONS_RE})\z/
              href = $1
              handle_bares($2, attr, "comma", href)
            when /\A(.*) \((#{SECTIONS_RE})\)\z/
              href = $1
              handle_bares($2, attr, "parens", href)
            when /\A([\w.]+)<(.*)\z/
              href = $2
              attr['section'] = $1
              attr['sectionFormat'] = 'bare'
            end
          end
          href = href.gsub(/\A[0-9]/) { "_#{$&}" } # can't start an IDREF with a number
          attr['target'] = href
          el = Element.new(:xref, nil, attr)
        end
        @tree.children << el
      end
      define_parser(:xref, XREF_START, '{{')

      IREF_START = /\(\(\((.*?)\)\)\)/u

      # Introduce new (((target))) syntax for irefs
      def parse_iref
        @src.pos += @src.matched_size
        href = @src[1]
        el = Element.new(:iref, nil, {'target' => href}) # XXX
        @tree.children << el
      end
      define_parser(:iref, IREF_START, '\(\(\(')

    end
  end

  class Element
    def rfc2629_fix
      if a = attr
        if anchor = a.delete('id')
          a['anchor'] = anchor
        end
        if anchor = a.delete('href')
          a['target'] = anchor
        end
      end
    end
  end

  module Converter

    # Converts a Kramdown::Document to HTML.
    class Rfc2629 < Base

      # we use these to do XML stuff, too
      include ::Kramdown::Utils::Html

      def el_html_attributes(el)
        html_attributes(el.attr)
      end
      def el_html_attributes_with(el, defattr)
        html_attributes(defattr.merge(el.attr))
      end

      # :stopdoc:

      # Defines the amount of indentation used when nesting XML tags.
      INDENTATION = 2

      # Initialize the XML converter with the given Kramdown document +doc+.
      def initialize(*doc)
        super
        @sec_level = 1
        @in_dt = 0
        @footnote_names_in_use = {}
      end

      def convert(el, indent = -INDENTATION, opts = {})
        if el.children[-1].type == :raw
          raw = convert1(el.children.pop, indent, opts)
        end
        "#{convert1(el, indent, opts)}#{end_sections(1, indent)}#{raw}"
      end

      def convert1(el, indent, opts = {})
        el.rfc2629_fix
        send("convert_#{el.type}", el, indent, opts)
      end

      def inner_a(el, indent, opts)
        indent += INDENTATION
        el.children.map do |inner_el|
          inner_el.rfc2629_fix
          send("convert_#{inner_el.type}", inner_el, indent, opts)
        end
      end

      def inner(el, indent, opts)
        inner_a(el, indent, opts).join('')
      end

      def convert_blank(el, indent, opts)
        "\n"
      end

      def convert_text(el, indent, opts)
        escape_html(el.value, :text)
      end

      def convert_p(el, indent, opts)
        if (el.children.size == 1 && el.children[0].type == :img) || opts[:unpacked]
          inner(el, indent, opts) # Part of the bad reference hack
        else
          "#{' '*indent}<t#{el_html_attributes(el)}>#{inner(el, indent, opts)}</t>\n"
        end
      end

      def saner_generate_id(value)
        generate_id(value).gsub(/-+/, '-')
      end

      SVG_COLORS = Hash.new {|h, k| k}
      <<COLORS.each_line {|l| k, v = l.chomp.split; SVG_COLORS[k] = v}
black	#000000
silver	#C0C0C0
gray	#808080
white	#FFFFFF
maroon	#800000
red	#FF0000
purple	#800080
fuchsia	#FF00FF
green	#008000
lime	#00FF00
olive	#808000
yellow	#FFFF00
navy	#000080
blue	#0000FF
teal	#008080
aqua	#00FFFF
COLORS

      def svg_munch_id(id)
        id.gsub(/[^-._A-Za-z0-9]/) {|x| "_%02X" % x.ord}
      end

      def self.hex_to_lin(h)
        h.to_i(16)**2.22        # approximating sRGB gamma
      end
      define_method :hex_to_lin, &method(:hex_to_lin)

      B_W_THRESHOLD = hex_to_lin("a4") # a little brighter than 1/2 0xFF -> white

      def svg_munch_color(c, fill)
        c = SVG_COLORS[c]
        case c
        when /\A#(..)(..)(..)\z/
          if hex_to_lin($1)*0.2126 + hex_to_lin($2)*0.7152 + hex_to_lin($3)*0.0722 >= B_W_THRESHOLD
            'white'
          else
            'black'
          end
        when 'none'
          'none' if fill        # delete for stroke
        else
          c
        end
      end

      def svg_clean(s)          # expensive, risky
        require "rexml/document"
        d = REXML::Document.new(s)
        REXML::XPath.each(d.root, "//*[@shape-rendering]") { |x| x.attributes["shape-rendering"] = nil }  #; warn x.inspect }
        REXML::XPath.each(d.root, "//*[@text-rendering]") { |x| x.attributes["text-rendering"] = nil }  #; warn x.inspect  }
        REXML::XPath.each(d.root, "//*[@stroke]") { |x| x.attributes["stroke"] = svg_munch_color(x.attributes["stroke"], false) }
        REXML::XPath.each(d.root, "//*[@fill]") { |x| x.attributes["fill"] = svg_munch_color(x.attributes["fill"], true) }
        REXML::XPath.each(d.root, "//*[@id]") { |x| x.attributes["id"] = svg_munch_id(x.attributes["id"]) }
##      REXML::XPath.each(d.root, "//rect") { |x| x.attributes["style"] = "fill:none;stroke:black;stroke-width:1" unless x.attributes["style"] }
        d.to_s
      end

      def memoize(meth, *args)
        require 'digest'
        Dir.mkdir(REFCACHEDIR) unless Dir.exists?(REFCACHEDIR)
        kdrfc_version = Gem.loaded_specs["kramdown-rfc2629"].version.to_s.gsub('.', '_') rescue "UNKNOWN"
        fn = "#{REFCACHEDIR}/kdrfc-#{kdrfc_version}-#{meth}-#{Digest::SHA256.hexdigest(Marshal.dump(args))[0...40]}.cache"
        begin
          out = Marshal.load(File.binread(fn))
        rescue StandardError => e
          # warn e.inspect
          out = method(meth).call(*args)
          File.binwrite(fn, Marshal.dump(out))
        end
        out
      end

      def capture_croak(t, err)
        if err != ''
          err.lines do |l|
            warn "*** [#{t}:] #{l.chomp}"
          end
        end
      end

      def svg_tool_process(t, result)
        require 'tempfile'
        file = Tempfile.new("kramdown-rfc")
        file.write(result)
        file.close
        case t
        when "goat"
          result1, err, _s = Open3.capture3("goat #{file.path}", stdin_data: result);
        when "ditaa"        # XXX: This needs some form of option-setting
          result1, err, _s = Open3.capture3("ditaa #{file.path} --svg -o -", stdin_data: result);
        when "mscgen"
          result1, err, _s = Open3.capture3("mscgen -T svg -i #{file.path} -o -", stdin_data: result);
        when "mermaid"
          result1, err, _s = Open3.capture3("mmdc -i #{file.path}", stdin_data: result); #  -b transparent
          outpath = file.path + ".svg"
          result1 = File.read(outpath)
          File.unlink(outpath)
        when "plantuml", "plantuml-utxt"
          plantuml = "@startuml\n#{result}\n@enduml"
          result1, err, _s = Open3.capture3("plantuml -pipe -tsvg", stdin_data: plantuml);
          result, err1, _s = Open3.capture3("plantuml -pipe -tutxt", stdin_data: plantuml) if t == "plantuml-utxt"
          err << err1
        when "math"
          result1, err, _s = Open3.capture3("tex2svg --font STIX --speech=false #{Shellwords.escape(' ' << result)}");
          result, err1, _s = Open3.capture3("asciitex -f #{file.path}")
          err << err1
        end
        capture_croak(t, err)
        # warn ["goat:", result1.inspect]
        file.unlink
        result1 = svg_clean(result1) unless t == "goat"
        result1, err, _s = Open3.capture3("svgcheck -qa", stdin_data: result1);
        capture_croak("svgcheck", err)
        # warn ["svgcheck:", result1.inspect]
        [result, result1]       # text, svg
      end

      def convert_codeblock(el, indent, opts)
        # el.attr['anchor'] ||= saner_generate_id(el.value) -- no longer in 1.0.6
        result = el.value
        blockclass = el.attr.delete('class')
        if blockclass == 'language-tbreak'
          result = result.lines.map {|line| [line.chomp, 0]}
          spaceind = 0
          result.each_with_index {|pair, index|
            if pair[0] == ''
              result[spaceind][1] += 1
              pair[0] = nil unless index == spaceind
            else
              spaceind = index
            end
          }
          # $stderr.puts(result.inspect)
          result = result.map {|line, space|
            "<![CDATA[#{line.gsub(/^\s+/) {|s| "\u00A0" * s.size}}]]><vspace blankLines=\"#{space}\"/>" if line
          }.compact.join("\n")
          "#{' '*indent}<t>#{result}</t>\n"
        else
          artwork_attr = {}
          t = nil
          if blockclass
            classes = blockclass.split(' ')
            classes.each do |cl|
              if md = cl.match(/\Alanguage-(.*)/)
                t = artwork_attr["type"] = md[1] # XXX overwrite
              else
                $stderr.puts "*** Unimplemented block class: #{cl}"
              end
            end
          end
          # compensate for XML2RFC idiosyncrasy by insisting on a blank line
          unless el.attr.delete('tight')
            result[0,0] = "\n" unless result[0,1] == "\n"
          end
          el.attr.each do |k, v|
            if md = k.match(/\Aartwork-(.*)/)
              el.attr.delete(k)
              artwork_attr[md[1]] = v
            end
          end
          case t
          when "goat", "ditaa", "mscgen", "plantuml", "plantuml-utxt", "mermaid", "math"
            result, result1 = memoize(:svg_tool_process, t, result)
            "#{' '*indent}<figure#{el_html_attributes(el)}><artset><artwork #{html_attributes(artwork_attr.merge("type"=> "svg"))}>#{result1.sub(/.*?<svg/m, "<svg")}</artwork><artwork #{html_attributes(artwork_attr.merge("type"=> "ascii-art"))}><![CDATA[#{result}#{result =~ /\n\Z/ ? '' : "\n"}]]></artwork></artset></figure>\n"
          else
            "#{' '*indent}<figure#{el_html_attributes(el)}><artwork#{html_attributes(artwork_attr)}><![CDATA[#{result}#{result =~ /\n\Z/ ? '' : "\n"}]]></artwork></figure>\n"
          end
        end
      end

      def convert_blockquote(el, indent, opts)
        text = inner(el, indent, opts)
        text = "<t></t>" unless text =~ /</ # empty block quote
        "#{' '*indent}<t><list style='empty'#{el_html_attributes(el)}>\n#{text}#{' '*indent}</list></t>\n"
      end

      def end_sections(to_level, indent)
        if indent < 0
          indent = 0
        end
        if @sec_level >= to_level
          delta = (@sec_level - to_level)
          @sec_level = to_level
          "#{' '*indent}</section>\n" * delta
        else
          $stderr.puts "Incorrect section nesting: Need to start with 1"
        end
      end

      def clean_pcdata(parts)    # hack, will become unnecessary with XML2RFCv3
        clean = ''
        irefs = ''
        # warn "clean_parts: #{parts.inspect}"
        parts.each do |p|
          md = p.match(%r{([^<]*)(.*)})
          clean << md[1]
          irefs << md[2]        # breaks for spanx... don't emphasize in headings!
        end
        [clean, irefs]
      end

      def convert_header(el, indent, opts)
        # todo: handle appendix tags
        el = el.deep_clone
        options = @doc ? @doc.options : @options # XXX: 0.11 vs. 0.12
        if options[:auto_ids] && !el.attr['anchor']
          el.attr['anchor'] = saner_generate_id(el.options[:raw_text])
        end
        if $options.v3
          if sl = el.attr.delete('slugifiedName') # could do general name- play
            attrstring = html_attributes({'slugifiedName' => sl})
          end
          irefs = "<name#{attrstring}>#{inner(el, indent, opts)}</name>" #
        else
        clean, irefs = clean_pcdata(inner_a(el, indent, opts))
        el.attr['title'] = clean
        end
        "#{end_sections(el.options[:level], indent)}#{' '*indent}<section#{@sec_level += 1; el_html_attributes(el)}>#{irefs}\n"
      end

      def convert_hr(el, indent, opts) # misuse for page break
        "#{' '*indent}<t><vspace blankLines='999' /></t>\n"
      end

      STYLES = {ul: 'symbols', ol: 'numbers', dl: 'hanging'}

      def convert_ul(el, indent, opts)
        opts = opts.merge(vspace: el.attr.delete('vspace'))
        attrstring = el_html_attributes_with(el, {"style" => STYLES[el.type]})
        if opts[:unpacked]
          "#{' '*indent}<list#{attrstring}>\n#{inner(el, indent, opts)}#{' '*indent}</list>\n"
          else
          "#{' '*indent}<t><list#{attrstring}>\n#{inner(el, indent, opts)}#{' '*indent}</list></t>\n"
        end
      end
      alias :convert_ol :convert_ul

      def convert_dl(el, indent, opts)
        if $options.v3
          if hangindent = el.attr.delete('hangIndent')
            el.attr['indent'] ||= hangindent # new attribute name wins
          end
          vspace = el.attr.delete('vspace')
          if vspace && !el.attr['newline']
            el.attr['newline'] = 'true'
          end
          "#{' '*indent}<dl#{el_html_attributes(el)}>\n#{inner(el, indent, opts.dup)}#{' '*indent}</dl>\n"
        else
          convert_ul(el, indent, opts)
        end
      end

      def convert_li(el, indent, opts)
        res_a = inner_a(el, indent, opts)
        if el.children.empty? || el.children.first.options[:category] == :span
          res = res_a.join('')
        else                    # merge multiple <t> elements
          res = res_a.select { |x|
            x.strip != ''
          }.map { |x|
            x.sub(/\A\s*<t>(.*)<\/t>\s*\Z/m) { $1}
          }.join("#{' '*indent}<vspace blankLines='1'/>\n").gsub(%r{(</list>)\s*<vspace blankLines='1'/>}) { $1 }.gsub(%r{<vspace blankLines='1'/>\s*(<list)}) { $1 }
        end
        "#{' '*indent}<t#{el_html_attributes(el)}>#{res}#{(res =~ /\n\Z/ ? ' '*indent : '')}</t>\n"
      end

      def convert_dd(el, indent, opts)
        if $options.v3
          out = ''
          if !opts[:haddt]
            out ="#{' '*indent}<dt/>\n" # you can't make this one up
          end
          opts[:haddt] = false
          out << "#{' '*indent}<dd#{el_html_attributes(el)}>\n#{inner(el, indent, opts)}#{' '*indent}</dd>\n"
        else
        output = ' '*indent
        if @in_dt == 1
          @in_dt = 0
        else
          output << "<t#{el_html_attributes(el)}>"
        end
        res = inner(el, indent+INDENTATION, opts.merge(unpacked: true))
#        if el.children.empty? || el.children.first.options[:category] != :block
          output << res << (res =~ /\n\Z/ ? ' '*indent : '')
#        else                    FIXME: The latter case is needed for more complex cases
#          output << "\n" << res << ' '*indent
#        end
        output << "</t>\n"
        end
      end

      def convert_dt(el, indent, opts) # SERIOUSLY BAD HACK:
        if $options.v3
          out = ''
          if opts[:haddt]
            out ="#{' '*indent}<dd><t/></dd>\n" # you can't make this one up
          end
          opts[:haddt] = true
          out << "#{' '*indent}<dt#{el_html_attributes(el)}>\n#{inner(el, indent, opts)}#{' '*indent}</dt>\n"
        else
        close = "#{' '*indent}</t>\n" * @in_dt
        @in_dt = 1
        vspace = opts[:vspace]
        vspaceel = "<vspace blankLines='#{vspace}'/>" if vspace
        ht = escape_html(inner(el, indent, opts), :attribute) # XXX this may leave gunk
        "#{close}#{' '*indent}<t#{el_html_attributes(el)} hangText=\"#{ht}\">#{vspaceel}\n"
        end
      end

      HTML_TAGS_WITH_BODY=['div', 'script']

      def convert_html_element(el, indent, opts)
        res = inner(el, indent, opts)
        if el.options[:category] == :span
          "<#{el.value}#{el_html_attributes(el)}" << (!res.empty? ? ">#{res}</#{el.value}>" : " />")
        else
          output = ''
          output << ' '*indent if !el.options[:parent_is_raw]
          output << "<#{el.value}#{el_html_attributes(el)}"
          if !res.empty? && el.options[:parse_type] != :block
            output << ">#{res}</#{el.value}>"
          elsif !res.empty?
            output << ">\n#{res}"  << ' '*indent << "</#{el.value}>"
          elsif HTML_TAGS_WITH_BODY.include?(el.value)
            output << "></#{el.value}>"
          else
            output << " />"
          end
          output << "\n" if el.options[:outer_element] || !el.options[:parent_is_raw]
          output
        end
      end

      def convert_xml_comment(el, indent, opts)
        if el.options[:category] == :block && !el.options[:parent_is_raw]
          ' '*indent + el.value + "\n"
        else
          el.value
        end
      end
      alias :convert_xml_pi :convert_xml_comment
      alias :convert_html_doctype :convert_xml_comment

      ALIGNMENTS = { default: :left, left: :left, right: :right, center: :center}
      COLS_ALIGN = { "l" => :left, "c" => :center, "r" => :right}

      def convert_table(el, indent, opts) # This only works for tables with headers
        alignment = el.options[:alignment].map { |al| ALIGNMENTS[al]}
        cols = (el.attr.delete("cols") || "").split(' ')
        "#{' '*indent}<texttable#{el_html_attributes(el)}>\n#{inner(el, indent, opts.merge(table_alignment: alignment, table_cols: cols))}#{' '*indent}</texttable>\n"
      end

      def convert_thead(el, indent, opts)
        inner(el, indent, opts)
      end
      alias :convert_tbody :convert_thead
      alias :convert_tfoot :convert_thead
      alias :convert_tr  :convert_thead

      def convert_td(el, indent, opts)
        if alignment = opts[:table_alignment]
          alignment = alignment.shift
          if cols = opts[:table_cols].shift
            md = cols.match(/(\d*(|em|[%*]))([lrc])/)
            if md[1].to_i != 0
              widthval = md[1]
              widthval << "em" if md[2].empty?
              widthopt = "width='#{widthval}' "
            end
            alignment = COLS_ALIGN[md[3]] || :left
          end
        end
        if alignment
          res, irefs = clean_pcdata(inner_a(el, indent, opts))
          warn "*** lost markup #{irefs} in table heading" unless irefs.empty?
          "#{' '*indent}<ttcol #{widthopt}align='#{alignment}'#{el_html_attributes(el)}>#{res.empty? ? "&#160;" : res}</ttcol>\n" # XXX need clean_pcdata
        else
          res = inner(el, indent, opts)
          "#{' '*indent}<c#{el_html_attributes(el)}>#{res.empty? ? "&#160;" : res}</c>\n"
        end
      end
      alias :convert_th :convert_td

      def convert_comment(el, indent, opts)
## Don't actually output all those comments into the XML:
#        if el.options[:category] == :block
#          "#{' '*indent}<!-- #{el.value} -->\n"
#        else
#          "<!-- #{el.value} -->"
#        end
      end

      def convert_br(el, indent, opts)
        "<vspace />"
      end

      def convert_a(el, indent, opts)
        gi = el.attr.delete('gi')
        res = inner(el, indent, opts)
        target = el.attr['target']
        if target[0] == "#"     # handle [](#foo) as xref as in RFC 7328
          el.attr['target'] = target = target[1..-1]
          if target.downcase == res.downcase
            res = ''            # get rid of raw anchors leaking through
          end
          gi ||= "xref"
        else
          gi ||= "eref"
        end
        "<#{gi}#{el_html_attributes(el)}>#{res}</#{gi}>"
      end

      def convert_xref(el, indent, opts)
        gi = el.attr.delete('gi')
        target = el.attr['target']
        if target[0] == "&"
          "#{target};"
        else
          if target =~ %r{\A\w+:(?://|.*@)}
            gi ||= "eref"
          else
            gi ||= "xref"
          end
          "<#{gi}#{el_html_attributes(el)}/>"
        end
      end

      def convert_contact(el, indent, opts)
        "<contact#{el_html_attributes(el)}/>"
      end

      REFCACHEDIR = ENV["KRAMDOWN_REFCACHEDIR"] || ".refcache"

      # warn "*** REFCACHEDIR #{REFCACHEDIR}"

      KRAMDOWN_OFFLINE = ENV["KRAMDOWN_OFFLINE"]
      KRAMDOWN_REFCACHE_REFETCH = ENV["KRAMDOWN_REFCACHE_REFETCH"]

      # this is now slightly dangerous as multiple urls could map to the same cachefile
      def get_and_cache_resource(url, cachefile, tvalid = 7200, tn = Time.now)
        fn = "#{REFCACHEDIR}/#{cachefile}"
        Dir.mkdir(REFCACHEDIR) unless Dir.exists?(REFCACHEDIR)
        f = File.stat(fn) rescue nil unless KRAMDOWN_REFCACHE_REFETCH
        if !KRAMDOWN_OFFLINE && (!f || tn - f.mtime >= tvalid)
          if f
            message = "renewing (stale by #{"%.1f" % ((tn-f.mtime)/86400)} days)"
            fetch_timeout = 10 # seconds, give up quickly if just renewing
          else
            message = "fetching"
            fetch_timeout = 60 # seconds; long timeout needed for Travis
          end
          $stderr.puts "#{fn}: #{message}"
          if ENV["HAVE_WGET"]
            `cd #{REFCACHEDIR}; wget -t 3 -T #{fetch_timeout} -Nnv "#{url}"` # ignore errors if offline (hack)
            begin
              File.utime nil, nil, fn
            rescue Errno::ENOENT
              warn "Can't fetch #{url} -- is wget in path?"
            end
          else
            require 'open-uri'
            require 'socket'
            require 'openssl'
            require 'timeout'
            begin
              Timeout::timeout(fetch_timeout) do
                options = {}
                if ENV["KRAMDOWN_DONT_VERIFY_HTTPS"]
                  options[:ssl_verify_mode] = OpenSSL::SSL::VERIFY_NONE
                end             # workaround for OpenSSL on Windows...
#               URI.open(url, **options) do |uf|          # not portable to older versions
                OpenURI.open_uri(url, **options) do |uf|
                  s = uf.read
                  if uf.status[0] != "200"
                    warn "*** Status code #{status} while fetching #{url}"
                  else
                    File.write(fn, s)
                  end
                end
              end
            rescue OpenURI::HTTPError, Errno::EHOSTUNREACH, Errno::ECONNREFUSED,
                   SocketError, Timeout::Error => e
              warn "*** #{e} while fetching #{url}"
            end
          end
        end
        begin
          File.read(fn) # this blows up if no cache available after fetch attempt
        rescue Errno::ENOENT => e
          warn "*** #{e} for #{fn}"
        end
      end

      # [subdirectory name, cache ttl in seconds, does it provide for ?anchor=]
      XML_RESOURCE_ORG_MAP = {
        "RFC" => ["bibxml", 86400*7], # these should change rarely
        "I-D" => "bibxml3",
        "W3C" => "bibxml4",
        "3GPP" => "bibxml5",
        "ANSI" => "bibxml2",
        "CCITT" => "bibxml2",
        "FIPS" => "bibxml2",
        # "IANA" => "bibxml2",   overtaken by bibxml8
        "IEEE" => "bibxml6",    # copied over to bibxml6 2019-02-27
        "ISO" => "bibxml2",
        "ITU" => "bibxml2",
        "NIST" => "bibxml2",
        "OASIS" => "bibxml2",
        "PKCS" => "bibxml2",
        "DOI" => ["bibxml7", 86400, true], # 24 h cache at source anyway
        "IANA" => ["bibxml8", 86400, true], # ditto
      }

      # XML_RESOURCE_ORG_HOST = ENV["XML_RESOURCE_ORG_HOST"] || "xml.resource.org"
      XML_RESOURCE_ORG_HOST = ENV["XML_RESOURCE_ORG_HOST"] || "xml2rfc.tools.ietf.org"
      XML_RESOURCE_ORG_PREFIX = ENV["XML_RESOURCE_ORG_PREFIX"] ||
                                "https://#{XML_RESOURCE_ORG_HOST}/public/rfc"

      KRAMDOWN_REFCACHETTL = (e = ENV["KRAMDOWN_REFCACHETTL"]) ? e.to_i : 3600

      def convert_img(el, indent, opts) # misuse the tag!
        if a = el.attr
          alt = a.delete('alt').strip
          alt = '' if alt == '!' # work around re-wrap uglyness
          if src = a.delete('src')
            a['target'] = src
          end
        end
        if alt == ":include:"   # Really bad misuse of tag...
          anchor = el.attr.delete('anchor') || (
            # not yet
            warn "*** missing anchor for '#{src}'"
            src
          )
          anchor.sub!(/\A[0-9]/) { "_#{$&}" } # can't start an ID with a number
          anchor.gsub!('/', '_')              # should take out all illegals
          to_insert = ""
          src.scan(/(W3C|3GPP|[A-Z-]+)[.]?([A-Za-z_0-9.\/\+-]+)/) do |t, n|
            fn = "reference.#{t}.#{n}.xml"
            sub, ttl, can_anchor = XML_RESOURCE_ORG_MAP[t]
            ttl ||= KRAMDOWN_REFCACHETTL  # everything but RFCs might change a lot
            puts "*** Huh: #{fn}" unless sub
            url = "#{XML_RESOURCE_ORG_PREFIX}/#{sub}/#{fn}"
            if can_anchor # create anchor server-side for stand_alone: false
              url << "?anchor=#{anchor}"
              fn[/.xml$/] = "--anchor=#{anchor}.xml"
            end
            to_insert = get_and_cache_resource(url, fn.gsub('/', '_'), ttl)
            to_insert.scrub! rescue nil # only do this for Ruby >= 2.1
            # this may be a bit controversial: Don't break the build if reference is broken
            if KRAMDOWN_OFFLINE
              unless to_insert
                to_insert = "<reference anchor='#{anchor}'> <front> <title>*** BROKEN REFERENCE ***</title> <author> <organization/> </author> <date/> </front> </reference>"
                warn "*** KRAMDOWN_OFFLINE: Inserting broken reference for #{fn}"
              end
            else
              exit 66 unless to_insert # EX_NOINPUT
            end
          end
          to_insert.sub(/<\?xml version=["']1.0["'] encoding=["']UTF-8["']\?>/, '')
            .sub(/\banchor=(?:"[^"]+"|'[^']+')/, "anchor=\"#{anchor}\"")
        else
          "<xref#{el_html_attributes(el)}>#{alt}</xref>"
        end
      end

      def convert_codespan(el, indent, opts)
        attrstring = el_html_attributes_with(el, {"style" => 'verb'})
        "<spanx#{attrstring}>#{escape_html(el.value)}</spanx>"
      end

      def convert_footnote(el, indent, opts) # XXX: footnotes into crefs???
        # this would be more like xml2rfc v3:
        # "\n#{' '*indent}<cref>\n#{inner(el.value, indent, opts).rstrip}\n#{' '*indent}</cref>"
        content = inner(el.value, indent, opts).strip
        content = escape_html(content.sub(/\A<t>(.*)<\/t>\z/m) {$1}, :text) # text only...
        name = el.options[:name].sub(/\A[0-9]/) {"_" << $&}
        while @footnote_names_in_use[name] do
          if name =~ /:\d+\z/
            name.succ!
          else
            name << ":1"
          end
        end
        @footnote_names_in_use[name] = true
        attrstring = el_html_attributes_with(el, {"anchor" => name})
        "\n#{' '*indent}<cref#{attrstring}>#{content}</cref>"
      end

      def convert_raw(el, indent, opts)
        end_sections(1, indent) +
        el.value + (el.options[:category] == :block ? "\n" : '')
      end

      EMPH = { em: "emph", strong: "strong"}

      def convert_em(el, indent, opts)
        if $options.v3
          gi = el.type
          "<#{gi}#{el_html_attributes(el)}>#{inner(el, indent, opts)}</#{gi}>"
        else
        attrstring = el_html_attributes_with(el, {"style" => EMPH[el.type]})
        span, irefs = clean_pcdata(inner_a(el, indent, opts))
        "<spanx#{attrstring}>#{span}</spanx>#{irefs}"
        end
      end
      alias :convert_strong :convert_em

      def convert_entity(el, indent, opts)
        entity_to_str(el.value)
      end

      TYPOGRAPHIC_SYMS = {
        :mdash => [::Kramdown::Utils::Entities.entity('mdash')],
        :ndash => [::Kramdown::Utils::Entities.entity('ndash')],
        :hellip => [::Kramdown::Utils::Entities.entity('hellip')],
        :laquo_space => [::Kramdown::Utils::Entities.entity('laquo'), ::Kramdown::Utils::Entities.entity('nbsp')],
        :raquo_space => [::Kramdown::Utils::Entities.entity('nbsp'), ::Kramdown::Utils::Entities.entity('raquo')],
        :laquo => [::Kramdown::Utils::Entities.entity('laquo')],
        :raquo => [::Kramdown::Utils::Entities.entity('raquo')]
      }
      def convert_typographic_sym(el, indent, opts)
        if (result = @options[:typographic_symbols][el.value])
          escape_html(result, :text)
        else
          TYPOGRAPHIC_SYMS[el.value].map {|e| entity_to_str(e) }.join('')
        end
      end

      def convert_smart_quote(el, indent, opts)
        entity_to_str(smart_quote_entity(el))
      end

      MATH_LATEX_FILENAME = File.expand_path '../../data/math.json', __FILE__
      MATH_LATEX = JSON.parse(File.read(MATH_LATEX_FILENAME, encoding: Encoding::UTF_8))
      MATH_REPLACEMENTS = MATH_LATEX["replacements"]
      MATH_COMBININGMARKS = MATH_LATEX["combiningmarks"]

      def munge_latex(s)
        MATH_REPLACEMENTS.each do |o, n|
          s.gsub!(o, n)
        end
        MATH_COMBININGMARKS.each do |m, n|
          re = /\\#{m[1..-1]}\{(\X)\}/
          s.gsub!(re) { "#$1#{n}" }
        end
        s
      end
      # XXX: This is missing sup/sub support, which needs to be added

      def convert_math(el, indent, opts) # XXX: This is wrong
        el = el.deep_clone
        if el.options[:category] == :block
          el.attr['artwork-type'] ||= ''
          el.attr['artwork-type'] += (el.attr['artwork-type'].empty? ? '' : ' ') + 'math'
          artwork_attr = {}
          el.attr.each do |k, v|
            if md = k.match(/\Aartwork-(.*)/)
              el.attr.delete(k)
              artwork_attr[md[1]] = v
            end
          end
          result, err, _s = Open3.capture3("tex2mail -noindent -ragged -by_par -linelength=69", stdin_data: el.value);
          # warn "*** tex2mail not in path?" unless s.success? -- doesn't have useful status
          capture_croak("tex2mail", err)
          "#{' '*indent}<figure#{el_html_attributes(el)}><artwork#{html_attributes(artwork_attr)}><![CDATA[#{result}#{result =~ /\n\Z/ ? '' : "\n"}]]></artwork></figure>\n"

        else
          type = 'spanx'
          if $options.v3
            type = 'contact'
            result = munge_latex(el.value)
            attrstring = el_html_attributes_with(el, {"fullname" => result.chomp, "asciiFullname" => ''})
          else
            warn "*** no support for inline math in XML2RFCv2"
            type = 'spanx'
            attrstring = el_html_attributes_with(el, {"style" => 'verb'})
            content = escape_html(el.value, :text)
          end
          "<#{type}#{attrstring}>#{content}</#{type}>"
        end
      end

      ITEM_RE = '\s*(?:"([^"]*)"|([^,]*?))\s*'
      IREF_RE = %r{\A(!\s*)?#{ITEM_RE}(?:,#{ITEM_RE})?\z}

      def iref_attr(s)
        md = s.match(IREF_RE)
        attr = {
          item: md[2] || md[3],
          subitem: md[4] || md[5],
          primary: md[1] && 'true',
        }
        "<iref#{html_attributes(attr)}/>"
      end

      def convert_iref(el, indent, opts)
        iref_attr(el.attr['target'])
      end

      def convert_abbreviation(el, indent, opts) # XXX: This is wrong
        title = @root.options[:abbrev_defs][el.value]
        title = nil if title.empty?
        value = el.value
        if item = title
          m = title.scan(Parser::RFC2629Kramdown::IREF_START)
          if m.empty?
            subitem = value
          else
            iref = m.map{|a,| iref_attr(a)}.join('')
          end
        else
          item = value
        end
        iref ||= "<iref#{html_attributes(item: item, subitem: subitem)}/>"
        "#{el.value}#{iref}"
      end

      def convert_root(el, indent, opts)
        result = inner(el, indent, opts)
      end

    end

  end
end
